Plastic trash bag with odor control and method of making

ABSTRACT

A plastic trash bag with odor control is formed of a bag having a pair of opposed sides joined together along longitudinal edges and at one end, the bag being longitudinally folded such that one bag side defines a pair of adjacent facing surfaces. A generally uniform dusting of odor-absorbing particles is disposed on at least the adjacent facing surfaces.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to plastic trash bags, and more particularly a plastic trash bag provided with odor control enhancements and a method of making a plastic trash bag with odor control enhancements.

[0002] Typically, plastic trash bags are formed by extruding a continuous tube of polyethylene plastic, from a molten source of a heated polyethylene blend, to form a “bubble” of polyethylene. The bubble is then cooled and collapsed to form a flat web of overlapping plies. The tubular envelope and web are continuously moved along a path from the extruder until the individual bags are sealed, perforated or severed, rolled and packaged.

[0003] There is a widespread belief in the plastic trash bag industry that the user or consumer of plastic trash bags considers the odor associated with trash bags and their use to be an undesirable characteristic. Obviously, odors may arise from a number of possible sources associated with plastic trash bags, such as the contents of the bag, the polyethylene material used to manufacture the bag, and residual matter on the inside of a can or container lined by the trash bag. Residual matter may not have been cleaned from the container after prior use.

[0004] One attempt to alleviate consumer dissatisfaction with odors associated with trash bags involved introducing substances carrying a perfumed scent into the polyethylene formulation from which the trash bags are extruded. These attempts merely mask the odor; they do not reduce the concentration or intensity of the odor. Such solutions typically require that the manufacturer provide a variety of different scents in order to meet consumer preferences. Even when scented material is present, it will mask primarily odors emanating from substances within the bag and, if the odor is produced by an unclean can, for example, scented bags may have less effectiveness in masking odors.

SUMMARY OF THE INVENTION

[0005] The present invention contemplates applying a generally uniform dusting of baking soda (sodium bicarbonate) or like odor-absorbing particles on at least the exterior surface of a tubular web of polyethylene or similar plastic during the process of manufacturing the bag. The baking soda is preferably applied by deposition from an electrostatic sprayer. The baking soda substantially uniformly coats at least one surface of the web prior to folding of the web longitudinally with the two coated half-surfaces adjacent and facing each other. The coated, folded web is then sealed, perforated and wound onto a roll or packed singly.

[0006] By applying the baking soda to one surface of the web and then folding the web before subsequent processing, the baking soda remains as a topical coating on what eventually will be a portion of the exterior surface of the bag. Subsequent processing—for example, pulling via nip rolls, supporting the web with fixed bars or rollers, sealing and perforating—does not disturb the baking soda because the baking soda coating is sandwiched between and protected by the longitudinally folded sides of the web. Thus, when the bag is unfolded for use, the baking soda is still present on a portion of the exterior surface of the bag. The baking soda is effective primarily to absorb and thereby reduce odors emanating from within the container in which the bag is placed for use and from the bag material itself. By applying the baking soda to both exterior surfaces of the web and then folding the web, the baking soda is not disturbed on a portion of the exterior surface of the bag, although it may be slightly disturbed on the other portion.

[0007] Moreover, one embodiment of the present invention contemplates incorporating odor-absorbing materials within the blend of polyethylene prior to extrusion of the tubular web. These chemicals are capable of absorbing, and therefore controlling, odors emanating from the contents within the bag. The combination of the exterior baking soda and odor-absorbing ingredients within the bag material cooperate to produce an effective overall reduction of unpleasant odors associated with a plastic trash bag and its use.

[0008] More particularly, the present invention encompasses a plastic trash bag comprising a bag having a pair of opposed sides joined together along longitudinal edges and at one end, the bag being longitudinally folded such that one bag side defines a pair of adjacent facing surfaces. A generally uniform dusting of odor-absorbing particles is disposed on the adjacent facing surfaces.

[0009] The other bag side is either relatively free of the odor-absorbing particles or defines a pair of oppositely facing surfaces, with a generally uniform dusting of odor-absorbing particles also being disposed on the oppositely facing surfaces. In a preferred embodiment, the odor-absorbing particles are baking soda (sodium bicarbonate) particles, preferably mixed with a relatively small quantity of a flow-control additive, and the bag is polyethylene, preferably polyethylene having a relatively small quantity of odor-absorbing material therein.

[0010] The present invention further encompasses a method of making a plastic trash bag in the form of a longitudinally folded flat tubular web sealed at one end. The method includes the step of applying, prior to longitudinal folding of the bag, a generally uniform dusting of odor-absorbing particles to one of the bag sides which will define a pair of adjacent facing surfaces after longitudinal folding of the bag.

[0011] In a preferred embodiment, the uniform dusting is applied immediately prior to longitudinal folding of the bag, and, after application of the uniform dusting, the bag is longitudinally folded and sealed at one end. The uniform dusting is applied electrostatically, preferably to only the one of the bag sides.

BRIEF DESCRIPTION OF THE DRAWING

[0012] The above and related object, features and advantages of the present invention will be more fully understood by reference to the following detailed description of the presently preferred, albeit illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawing wherein:

[0013]FIG. 1 is a diagrammatic or schematic view of a plastic bag manufacturing line for practice of the present invention;

[0014]FIG. 2 is a diagrammatic view of an electrostatic spray applicator for applying baking soda to the moving web, as seen in FIG. 1; and

[0015]FIG. 3 is a fragmentary diagrammatic or schematic view of an alternative plastic bag manufacturing line for practice of the present invention.

[0016] Like reference numerals will be used to refer to like parts in the various views.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

[0017] Referring to FIG. 1, there is shown, partially in diagrammatic or schematic form, apparatus for making plastic bags, the apparatus being commonly referred to in the industry as a “blown film line.” Such facilities are large and typically rest on a floor, as represented by the horizontal line 10. The drawing of the blown film line of FIG. 1 includes only those principal parts to which reference need be made to understand the present invention. Moreover, except for the baking soda applicator incorporated into the blown film line and specifically illustrated in FIG. 2, the apparatus shown in FIG. 1 is otherwise conventional and known to persons skilled in this art. Thus, a more detailed description of the structure and components of the apparatus such as a drive motor, controls, transmission, etc. need not be given for an understanding of the present invention by those skilled in the art.

[0018] Hopper 11 contains a blend of polyethylene material and suitable additives out of which the bags are made. Conventional LLD (linear low density) polyethylene material, including conventional coloring concentrates, slip and calcium carbonate in known quantities and percentages, provide the basic blend. To this mixture is added, in the preferred embodiment of the present invention, an odor-absorbing material in the range of 2-6 percent by weight of the combined polyethylene blend. A suitable odor-absorbing additive is molecular sieves known as gas absorber concentrate, and in particular, a product available under the tradename GAG-1000-3 from Polyfil Corp. of Rockaway, N.J. Another suitable odor-absorbing additive is available under the tradename Code PM 111 76E4 from Techmer PM of Rancho Dominguez, Calif.

[0019] The blend is fed from hopper 11 into a horizontal extruder 12, where it is heated to approximately 400° F. From the extruder 12, the molten blend is forced through a vertically elongated die 13 which forms the molten material into a continuous tube of closed cross-section about a core of compressed air. Then the tube is passed through an air ring which forces chilled air onto the exterior of the tube.

[0020] After the polyethylene tube exits the vertically elongated die, it forms a continuous enlarged cylindrical structure referred to as a “bubble” in the industry. The bubble is formed and expanded by compressed air. As the polyethylene tube travels vertically in the form of a cylindrical bubble, the polyethylene material cools and increases in rigidity and strength. The polyethylene tube continues to travel at a constant speed and constant tension, driven by a set of primary nip rolls (and other nip rolls which are controlled to follow the primary nip rolls) to maintain a constant tension on the material throughout the process (nip rolls not shown).

[0021] The polyethylene tube then enters a device 20 referred to in the industry as an “A-frame structure.” The A-frame 20 includes opposed first and second side planar members which are open at the base to receive the bubble and then converge inwardly in the form of an “A” to form a narrow exit slot at the top. The polyethylene tube, as it moves upwardly, eventually contacts the opposing inner surfaces of the side members of the A-frame. The side members thereupon transition the cylindrical cross-section of the tube initially to an elliptical shape and cross-section, and eventually to a planar shape, collapsing the tube to a flat web configuration comprising two overlying, contacting plies. The collapsed web-like tube exists the A-frame 20, being pulled by the pair of primary nip rolls.

[0022] Eventually, the web enters a folding frame 50 which folds the web longitudinally—that is, so that the edges of the flattened web are brought to overlie one another, creating a four-ply web with a first lateral edge formed by the two original edges of the two-ply web and a second lateral edge which is the folded longitudinal centerline of the original two-ply web.

[0023] After leaving the folding frame 50, the web enters a second or exit set of nip rolls (not shown) preceded by a tension-maintaining apparatus (not shown) which maintains a substantially constant tension on the web between the primary nip rolls and the exit nip rolls.

[0024] After the web leaves the exit nip rolls, it passes through a bag machine 60 which applies the bottom seal (or “heat weld”) by means of a heated bar on a rotating cylinder, as is generally known. As the heat seal is applied to the web after it is longitudinally folded, it produces a heat welding of the gathered bag material. Thus, the web comprises four overlapping plies when the heat weld is applied. This produces a bag bottom which has a so-called “flat bottom” configuration. A perforation (providing a tear line between adjacent bags) is also provided before the web leaves the bag machine 60.

[0025] The web then passes through a winder 70 where it is wound into a coreless roll. The rolls are then removed from or ejected by the winder, and placed into a carton or a sleeve for packaging. Alternatively, the web may be wound on cores, if desired.

[0026] As earlier indicated, the “blown film line” as described hereinabove is conventional in the art for production of a flat bottom bag.

[0027] The “blown film line” is also conventional in the art for production of a bag with a “star bottom” configuration which is believed to provide a greater strength in the bottom of the bag and a more uniform, reliable seal than the flat bottom configuration. The blown film line is substantially as described above except that, as the bubble travels through the A-frame structure 20, the bubble also travels over opposing gusset boards which fold the lateral sides of the bubble inward to form two facing (almost contacting) gussets. Thus, instead of a flat web configuration comprising two overlying contacting plies, the tube leaving the A-frame 20 comprises four overlying contacting plies, the two additional tube plies being formed by the gusset folds. The web is folded over once more by the folding frame 50 to create an eight-ply web instead of the four-ply web described above. While the gusset folds are clearly exterior surfaces of the bag when the bag is in use and typically form 50% of the exterior surface of the bag in use (excluding the bottom), during the travel of the bag along the blown film line the gussets are “hidden” by the exterior surface of the bag and may be ignored for the purposes of the present invention. Accordingly, the present invention will be described hereinbelow in the context of a flat bottom bag, although clearly the principles thereof are equally applicable to a star bottom bag.

[0028] According to one preferred embodiment of the present invention, prior to entering the folding frame 50, the web passes an applicator 40, to be described further below, which applies particulate sodium bicarbonate (NaHCO₃, commonly called “baking soda”) in the form of dispersed individual particles shown at 43, to one surface of the double-ply web, in the region designated 42, but only on the side of the web adjacent the applicator 40. The one surface of the double-ply web is coated with baking soda particles substantially uniformly and completely. Thereafter, the web is folded longitudinally in the folding frame 50, as described above, so that the coated half-surfaces are facing and the baking soda particles thereon will not be disturbed (e.g. removed) by further processing.

[0029] Sufficient coating of the web with baking soda may be achieved by placing the applicator 40 further upstream of the folding frame 50, but it is preferred to locate the applicator 40 immediately upstream of, and adjacent to, the folding frame 50, as illustrated. The reason for this is to avoid having the baking soda-coated surface of the web contact any guide roller or pass through nip rollers. Any contact with rollers may create a tendency to deposit the baking soda on the rollers, and, because of its nature, the baking soda would tend to cake and obstruct the free movement of the web through such rollers. By folding the web immediately after applying the baking soda thereto, the uniformity of the applied coat is maintained, even though the web may undergo subsequent handling or processing. In particular, contact between the baking soda and rollers is avoided in this manner.

[0030] On the other hand, it is also advantageous to apply the baking soda to the web shortly after it is cooled (for example, while it is still about 120° F.) so that the baking soda particles become “stuck” on the warm bag and thus are less likely to become dislodged therefrom by subsequent processing of the web. Optimum placement of the applicator 40 downstream of the A-frame 20 and upstream of the folding frame 50 may be empirically determined for any given blown film line with a minimum of routine experimentation.

[0031] Referring now to FIG. 3, where it is not necessary to form a bottom of the bag by first folding the web and then heat-welding the bottom, the bottom of the bag material may be heat-welded (and, if desired, perforated) in a bag machine 60A before entering the folding frame 50A, in which case the applicator 40A is preferably still placed immediately upstream of the folding frame 50A, but in this example downstream of the welding and perforating operation sites of the bag machine 60A.

[0032] Where deposition of the baking soda on the rollers is not deemed to be problematic, the baking soda may be applied to both surfaces of the double-ply web. This may be done by use of a single applicator 40 positioned to distribute the baking soda substantially uniformly and completely on both surfaces of the double-ply web or by use of two applicators, the applicator 40 as described hereinabove and a second like applicator 40′ (indicated in phantom line in FIG. 1) for substantially uniformly and completely coating with baking soda the opposite surface of the double-ply web. This applicator 40′ applies the particulate sodium bicarbonate in the form of dispersed individual particulates to the opposite surface of the double-ply web, so that both surfaces of the double-ply web become substantially uniformly and completely coated with baking soda particulates.

[0033] In those instances where the possible adverse effects of contact between the rollers and the baking soda are not anticipated—that is, there is no adverse effect on the rollers due to the deposition of baking soda thereon from the web and there is no disturbance of the uniform and complete coating of the baking soda on the web by contact with the rollers—the applicator 40 or applicators 40, 40′ may be located anywhere after formation of the double-ply web. However preferably the applicator 40 is disposed immediately prior to the folding frame 50, and the applicator 40′ is disposed immediately prior to the bag machine 60 or, as illustrated, winder 70. Preferably applicator 40′ is downstream of applicator 40 and preferably downstream from as much as possible of the blown film line equipment as possible. Applicator 40′ is illustrated in FIG. 1 as being disposed after the folding frame 50 and bag machine 60 and just before the winder 70.

[0034] While a single applicator 40 may be used to apply the baking soda simultaneously to both exposed surfaces of the double-ply web, preferably a pair of applicators 40, 40′ are used, one deployed on either side of the moving web, one upstream of the other.

[0035] Where desired, baking soda may also be applied to the interior of the bag to assist in neutralization of odors emanating from the materials placed within the bag.

[0036] The baking soda is suitably applied to the web by an electrostatic sprayer to be described further below. The advantages of using an electrostatic applicator are that the particles of baking soda are uniformly dispersed and therefore applied in a more uniform coating. Further, the electrostatically charged particles have a greater tendency to adhere to the polyethylene material of the bag due to the electrostatic attraction force.

[0037] Turning now to FIG. 2, one form of applicator 40 is shown. The applicator of FIG. 2 is referred to in the industry as an “electrostatic sprayer,” and it is commercially available under the tradename Series 500 Electrostatic Sprayer from Oxy-Dry Corporation of Itasca, Ill. The applicator 40 includes an enclosed hopper or housing 54 which provides a hopper for a supply of the baking soda powder. Bridging or caking of the powder within housing 54 is prevented by an internal air blower (not shown). An etched roller 55 is mounted within the housing 54 and driven by a motor (not shown) to rotate in a clockwise direction.

[0038] The surface of the roller 55 is etched to form a series of spaced pockets or cells of uniform size and spacing. The cells pass beneath the supply of baking soda powder in hopper 54 as the roller 55 rotates and becomes filled with baking soda. A doctor blade (not shown) removes excess powder from the cells as the roller 55 rotates. Thus, the etched roller 55 accurately meters the delivery of baking soda. The interior of the housing 54 is pressurized and provides air flow, referred to as an “air curtain,” to assist in delivering the powder to the desired area 42 of the moving web.

[0039] As the roller 55 rotates, it passes by a tube 57, referred to as a “blast-off” tube, which applies an electrostatic charge to the powder in the etched cells. The powder is then delivered from the roller 55 as a stream of separated, charged particles 43, attracted to the moving web by the electrostatic charge. The particles 43 are deposited on the web in an uniform coating, and they adhere to the web due to the electrostatic charge.

[0040] As the roller 55 continues to rotate, it passes a second tube 59 which forces pressurized air against the surface of the roller 55 to remove any residual powder and thereby prevent build-up of powder on the surface of the roller 55.

[0041] A suitable baking soda for use with the electrostatic sprayer is available under the tradename Product Code 3DF Baking Soda from Church & Dwight Corporation. Preferably 0.5-3.0 percent fumed silica is added as a flow control additive. A suitable flow control additive is available under the tradename Product Code TS-610 Treated Fumed Silica from Cabot Corporation.

[0042] While electrostatic applicators are preferred, clearly non-electrostatic applicators may alternatively be used in the practice of the present invention.

[0043] While the principles of the present invention have been shown and described in connection with the formation of a bag by the “bubble” technique, clearly the principles of the present invention may be applied as well to bags formed by other techniques as well. Thus, the principles apply to bags formed by the “cast” technique, wherein a flat sheet of plastic material is laid out, folded longitudinally, and the edges then welded shut to form a web. The web is subsequently passed through a folding frame, a bag machine and a winder. Use of the cast technique facilitates the application of the baking soda to the interior of bag (prior to the longitudinal folding of the sheet of plastic material and the subsequent welding of the longitudinal edges) as well as the application of the baking soda to the exterior of the bag. Manufacture of a bag by the cast technique is conventional in the art and, accordingly, need not be described herein in further detail.

[0044] While the principles of the present invention have been expounded above with regard to plastic trash bags, clearly they are also applicable to plastic films (not bags) of the type conventionally used to wrap articles such as foods. The film is preferably polyethylene, polypropylene or polystyrene. Depending upon the particular articles to be wrapped, a generally uniform dusting of the baking soda particles is disposed on a surface of the film (the surface facing the article, the surface facing away from the article, or both). When the article is a foodstuff, preferably the dusting is disposed only on one surface of the film.

[0045] Now that the preferred embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. the spirit and scope of the present invention is to be construed broadly and limited only by the appended claims, and not by the foregoing specification. 

I claim:
 1. A plastic trash bag comprising: (A) a bag having a pair of opposed sides joined together along longitudinal edges and at one end, said bag being longitudinally folded such that one bag side defines a pair of adjacent facing surfaces; and (B) a generally uniform dusting of odor-absorbing particles on said adjacent facing surfaces.
 2. The bag of claim 1 wherein the other bag side is relatively free of said odor-absorbing particles.
 3. The bag of claim 1 wherein the other bag side defines a pair of oppositely facing surfaces, and a generally uniform dusting of odor-absorbing particles is also disposed on said oppositely facing surfaces.
 4. The bag of claim 1 wherein said odor-absorbing particles are baking soda (sodium bicarbonate) particles.
 5. The bag of claim 1 wherein said odor-absorbing particles are baking soda particles mixed with a relatively small quantity of a flow-control additive.
 6. The bag of claim 1 wherein said bag is polyethylene.
 7. The bag of claim 1 wherein said bag is polyethylene having a relatively small quantity of odor-absorbing material therein.
 8. A plastic trash bag comprising: (A) a polyethylene bag having a pair of opposed sides joined together along longitudinal edges and at one end, said bag being longitudinally folded such that one bag side defines a pair of adjacent facing surfaces; and (B) a generally uniform dusting of odor-absorbing baking soda particles on said adjacent facing surfaces, the other bag side being relatively free of said odor-absorbing particles.
 9. A method of making a plastic trash bag in the form of a longitudinally folded flat tubular web sealed at one end, the method including the step of applying, prior to longitudinal folding of the bag, a generally uniform dusting of odor-absorbing particles to one of the bag sides which will define a pair of adjacent facing surfaces after longitudinal folding of the bag.
 10. The method of claim 9 wherein the uniform dusting is applied immediately prior to longitudinal folding of the bag.
 11. The method of claim 9 wherein, after application of the uniform dusting, the bag is longitudinally folded and sealed at one end.
 12. The method of claim 9 wherein the uniform dusting is applied electrostatically.
 13. The method of claim 9 wherein the uniform dusting is applied to only the one of the bag sides.
 14. The method of claim 9 wherein the odor-absorbing particles are baking soda (sodium bicarbonate) particles.
 15. The method of claim 9 wherein the odor-absorbing particles are baking soda particles mixed with a relatively small quantity of a flow-control additive.
 16. The method of claim 9 wherein the bag is polyethylene.
 17. The method of claim 9 wherein the bag is polyethylene having a relatively small quantity of odor-absorbing material therein.
 18. A method of making a plastic trash bag in the form of a longitudinally folded flat tubular web of polyethylene sealed at one end, the method including the step of electrostatically applying, immediately prior to longitudinal folding of the bag, a generally uniform dusting of odor-absorbing baking soda particles to only the one of the bag sides which will define a pair of adjacent facing surfaces after longitudinal folding of the bag.
 19. The method of claim 18 wherein a generally uniform dusting of odor-absorbing particles is applied to exposed surfaces of the bag subsequent to longitudinal folding of the bag.
 20. A wrap comprising a plastic film having on at least one surface thereof a generally uniform dusting of odor-absorbing baking soda particles.
 21. The wrap of claim 20 wherein said film has said dusting on each surface thereof.
 22. The wrap of claim 20 wherein said film has said dusting on only one surface thereof. 